Shuttle Q&A Part 5

• #2620 by HelixSpiral on 13 May, 2012 14:16
• Thanks, alk. Being a computer guy, the software and GPCs had always interested me and I always like reading your posts.
• #2621 by DaveS on 14 May, 2012 00:52
• Anyone know the Z_o coordinates for the bottom of the PLB bays?  I don't mean the floor of the midbody, but just the bays that give the payload bay the familiar semi-circular shape. According to the Mechanical Systems Workbook, the sill longerons are at Z_o410.00.
• #2622 by Fequalsma on 14 May, 2012 01:25
• 305 or 308.4 per the diagram above.  it says the longerons are at 414...
  
  
  

  Quote from: DaveS on 14 May, 2012 00:52

  Anyone know the Z_o coordinates for the bottom of the PLB bays?  I don't mean the floor of the midbody, but just the bays that give the payload bay the familiar semi-circular shape. According to the Mechanical Systems Workbook, the sill longerons are at Z_o410.00.
  
• #2623 by alk3997 on 14 May, 2012 02:45
• Quote from: HelixSpiral on 13 May, 2012 14:16

  Thanks, alk. Being a computer guy, the software and GPCs had always interested me and I always like reading your posts.
  

  
  Your welcome and I'm glad you find the appends interesting.  Sorry I don't get too much time anymore to answer these (now) historical questions.
  
  Andy
• #2624 by DaveS on 14 May, 2012 03:30
• Quote from: Fequalsma on 14 May, 2012 01:25

  305 or 308.4 per the diagram above.  it says the longerons are at 414...
  
  
  

  Quote from: DaveS on 14 May, 2012 00:52

  Anyone know the Z_o coordinates for the bottom of the PLB bays?  I don't mean the floor of the midbody, but just the bays that give the payload bay the familiar semi-circular shape. According to the Mechanical Systems Workbook, the sill longerons are at Z_o410.00.
  

  I don't think Z_o414.0 is for the longerons but rather payload bay door hinge line. Based on my research the PLBD door hinge lines are at Y_o±95 with the longerons at Y_o±90. And the shape of the longerons from bottom to top roughly corresponds to a 5" square.
• #2625 by DaveS on 15 May, 2012 23:37
• Anyone know if the encircled brackets in the attached photo is equally spaced along the length of the PLB longerons or if it varies? Also, any ideas what the metal cylinder in the photo is for? I'm thinking it's a drive rod of sorts for the MPMs.

  ---

  
• #2626 by NavySpaceFan on 21 May, 2012 22:09
• Was the solar array that slipped its tensioning cables during STS-97 the same one that jammed during 116 and tore during 120?
• #2627 by sivodave on 24 May, 2012 09:10
• Hi All.
  
  Question of the day is: was there any difference between the APDS used for docking to the MIR and the one used for docking to the ISS?
  
  Thanks very much
  
  Davide
• #2628 by iskyfly on 24 May, 2012 19:18
• Thank you alk3997 for your reply re: GPS errors during roll out.
  
  
• #2629 by Spaceguy5 on 08 Jun, 2012 20:40
• Why are the blankets in the aft of Endeavour's payload bay different from the rest of the orbiters?
  
  For example, this blanket (VO70-362609-058): If you look at one up close, it has a velcro flap, a set of flaps with snap buttons, and a snap-shut hole in the middle. The blanket on the opposite side also has similar features.
  
  Similarly, this blanket (VO70-362610-042) as well as it's twin... if you look up close, they both also have a velcro flap.
• #2630 by Archer on 11 Jun, 2012 18:59
• How much time does it take to inspect Space Shuttle TPS tiles after the flight and repair it (damaged ones are replaced I guess)?
• #2631 by Jim on 11 Jun, 2012 19:02
• Quote from: Archer on 11 Jun, 2012 18:59

  How much time does it take to inspect Space Shuttle TPS tiles after the flight and repair it (damaged ones are replaced I guess)?
  

  
  Most of the time between missions.
• #2632 by Archer on 11 Jun, 2012 19:46
• Quote from: Jim on 11 Jun, 2012 19:02

  Quote from: Archer on 11 Jun, 2012 18:59

  How much time does it take to inspect Space Shuttle TPS tiles after the flight and repair it (damaged ones are replaced I guess)?
  

  
  Most of the time between missions.
  

  Thank you!
• #2633 by Archer on 11 Jun, 2012 22:08
• Quote from: Jim on 11 Jun, 2012 19:02

  Quote from: Archer on 11 Jun, 2012 18:59

  How much time does it take to inspect Space Shuttle TPS tiles after the flight and repair it (damaged ones are replaced I guess)?
  

  
  Most of the time between missions.
  

  What takes more time: inspection or repairs?
• #2634 by sivodave on 13 Jun, 2012 18:51
• Hi all.
  
  one question about deorbit burn.
  
  Which is the reason for which during the deorbit the Orbiter was placed with the belly up? As long as you have tail-first is shouldn't be important if the belly is up or down, right?
  
  My guess is that in this was, at completion of the burn it would have been faster maneuvering to the entry attitude of 40 degrees of angle of attack and that maybe in this way the pilots had a better situation awarness.
  
  What do you think?
  
  Thanks very much
  
  Davide
• #2635 by wolfpack on 13 Jun, 2012 19:22
• Quote from: sivodave on 13 Jun, 2012 18:51

  Hi all.
  
  one question about deorbit burn.
  
  Which is the reason for which during the deorbit the Orbiter was placed with the belly up? As long as you have tail-first is shouldn't be important if the belly is up or down, right?
  
  My guess is that in this was, at completion of the burn it would have been faster maneuvering to the entry attitude of 40 degrees of angle of attack and that maybe in this way the pilots had a better situation awarness.
  
  What do you think?
  
  Thanks very much
  
  Davide
  

  
  If the deorbit burn is roughly halfway around the planet from entry interface, then the "belly-up" burn will have the Orbiter in (or near) the proper reentry attitude.
  
  At burn = Orbiter "top" towards Earth
  At halfway point = Orbiter "nose" towards Earth
  At EI = Orbiter "belly" towards Earth
  
  Remember the only reason the Orbiter orbits the Earth with its "top" pointed toward Earth is because it has been imparted with a pitch motion with period equal to the orbital period. Without that it would be a cycle of "nose"/"top"/"tail"/"belly" (or the reverse).
  
  I hope that wasn't too basic of an answer due to me misunderstanding the question.
• #2636 by sivodave on 13 Jun, 2012 22:09
• Hi wolfpack.
  
  I kept reading a little bit about this subject and I think I've now understood what you are saying. So if my understanding is correct, the reason is that for all duration of coasting from deorbit burn to EI, the Orbiter kept an inertial attitude.
  
  If this is the case, I've though another question. Maneuvering to burn attitude was done 20 minutes before the burn. If the orbiter kept this attitude inertially, does this not mean that the burn was not completely along the +x axis, but had also a +z component?
  
  or the inertial attitude was kept only AFTER the deorbit burn, while up to the deorbit burn the Orbiter had a LVLH attitude?
  
  Thanks very much
  
  Davide
• #2637 by wolfpack on 15 Jun, 2012 14:10
• Quote from: sivodave on 13 Jun, 2012 22:09

  Hi wolfpack.
  
  I kept reading a little bit about this subject and I think I've now understood what you are saying. So if my understanding is correct, the reason is that for all duration of coasting from deorbit burn to EI, the Orbiter kept an inertial attitude.
  
  If this is the case, I've though another question. Maneuvering to burn attitude was done 20 minutes before the burn. If the orbiter kept this attitude inertially, does this not mean that the burn was not completely along the +x axis, but had also a +z component?
  
  or the inertial attitude was kept only AFTER the deorbit burn, while up to the deorbit burn the Orbiter had a LVLH attitude?
  
  Thanks very much
  
  Davide
  

  
  Perhaps the maneuver was done such that the attitude was for a completely +x burn at TIG? I'm not sure, this will have to be answered by Jorge or someone else with the expertise.
  
  My assumption (which is probably incorrect) is that things are done to minimize propellant consumption.
• #2638 by SiameseCat on 17 Jun, 2012 13:30
• Quote from: wolfpack on 15 Jun, 2012 14:10

  Quote from: sivodave on 13 Jun, 2012 22:09

  Hi wolfpack.
  
  I kept reading a little bit about this subject and I think I've now understood what you are saying. So if my understanding is correct, the reason is that for all duration of coasting from deorbit burn to EI, the Orbiter kept an inertial attitude.
  
  If this is the case, I've though another question. Maneuvering to burn attitude was done 20 minutes before the burn. If the orbiter kept this attitude inertially, does this not mean that the burn was not completely along the +x axis, but had also a +z component?
  
  or the inertial attitude was kept only AFTER the deorbit burn, while up to the deorbit burn the Orbiter had a LVLH attitude?
  
  Thanks very much
  
  Davide
  

  
  Perhaps the maneuver was done such that the attitude was for a completely +x burn at TIG? I'm not sure, this will have to be answered by Jorge or someone else with the expertise.
  
  My assumption (which is probably incorrect) is that things are done to minimize propellant consumption.
  

  That's correct; a constant inertial attitude means that the shuttle is always rotating in an LVLH frame. The inertial burn attitude will result in the correct LVLH attitude at TIG.
  
  I think an inertial burn is actually more efficient than an LVLH burn, because you're always thrusting in the same direction. If you think about an LVLH burn, the direction is changing, so the thrust at the end of the burn partially cancels out the thrust at the start of the burn.
  
  For deorbit burns, it's possible to deliberately waste propellant by burning out-of-plane. This reduces the shuttle's landing weight.
  
• #2639 by sivodave on 20 Jun, 2012 08:32
• Thanks SiameseCat. I think now I've understood how it worked the deorbit burn.
  
  Davide